Mechanical fasteners are experiencing renewed popularity in the manufacturing industry in assembly operations. This is due in part to various governmental requirements that certain products, such as automobiles, be designed for disassembly at the end of their useful life to facilitate separation of dissimilar materials and thereby promote recycling or reuse of the materials. While there seems to be no end in sight to the innovation of new joining techniques, it has proven difficult to improve on the tried-and-true threaded fastener when it comes to attaching parts together in a way that is robust in the long-term, yet ultimately temporary.
While fastener manufacturers may rejoice in the renewed interest in their wares, the personnel who must use such fasteners in assembly operations will not. Mechanical fasteners have long been a nemesis of assembly line foremen and plant managers the world over. They are small, tedious to handle, and notorious for jamming-up automated manufacturing equipment and causing downtime a cross-threaded or misfed screw can shut down an entire assembly line and quickly eat into the efficiency and profitability of an assembly operation.
One problem with mechanical fasteners is the bulk form in which they are typically delivered and/or stored prior to use. Fasteners are typically piled together randomly in a bin or box by the hundreds, thousands, or tens of thousands. At some point during the life of an individual mechanical fastener, it must be reoriented from its randomly acquired storage orientation to a desired orientation for use. To achieve this, vibratory bowl feeders have become ubiquitous fixtures in assembly operations. British Patent No. 993,645 to Hoefliger et al. discloses an example of a vibratory bowl feeder that consists of a round bowl with a narrow ramp spiraling up the inner wall of the bowl. As the bowl vibrates, the parts to be fed are conveyed up the ramp from an end in or near the bulk fasteners and arrive at a dispensing end near the top of the bowl in a single-file arrangement. These bowls usually include orienting features (e.g., angled protrusions, openings in the ramp, etc.) located along the ramp that are designed to reorient passing fasteners and/or send misoriented fasteners back to the bottom of the bowl for refeeding.
While such feeders offer some advantages over manual sorting and placement, they come with their own sets of problems. For one, each bowl feeder is specifically designed for one particular fastener size and geometty, any fastener change thus requires a new feeder bowl design. Vibratory feeders are also infamous for becoming jammed, due to an inevitable burr or other imperfection or a stray fastener of different size or geometry. Indeed, assembly plants with large numbers of bowl feeders often have personnel dedicated to clearing jams. There are also physical limitations on the speed at which fasteners can be fed by these devices.